Present incline or stair-climbing exercise art teaches a constant rate of descent of the downward moving step under weight of the user. These teachings are best elucidated by U.S. Pat. Nos. 3,592,466; 3,529,474; and 3,970,302 issued respectively to Parson, Olson and McFee. They do not provide for a slowing of a portion of the downward step movement to facilitate "step-up", and as a result, lose a portion of the advantage that stair or incline climbing has in comparison with other exercises. This lost advantage is important, becoming larger and more important as the exercise intensity level increases with increased stepping rate or frequency.
The advantage obtained by exercising through climbing an incline as opposed to moving on a level surface is that on the incline greater energy expenditure rates can be obtained with less velocity. Research on energy expenditure rates for walking/running on the level and on an lincline has produced the Bobbert equation: EQU Log.sub.10 H=Log.sub.10 W 0.004591V+0.024487.theta.+0.0002659 V.theta.
By examination of this formula that relates energy expended (H) with body weight (W), velocity (V), clamping angle (.theta.), it can be seen when the climbing angle is zero, the velocity required for any significant energy expenditure is higher than when the slope (.theta.) is positive.
This velocity reduction when exercising on an incline is turned into comfort by stair-climbing exercise equipment, allowing uses to exercise at higher levels for shorter periods of time. However, in observing exercisers using existing stair-climbing simulation equipment at various climbing rates, and in reviewing resulting physiological indicators such as oxygen consumption, it is noticeable that the amount of vertical displacement of the user's center of gravity (c.g.) in respect to the earth that occurs with each step is decreased as the stepping rate (velocity) is increased. At very low stepping rates the displacement of the user's c.g. is essentially that of the height difference between the lowest position of the step and its highest position. At very high stepping rates, the user's c.g. displacement is near zero. Moreover, the rate of oxygen consumed, which is the accepted index of exercise cardio-vascular benefit drops in relation to the stepping rate.
In walking or running on an incline, the activity that the subject equipment is simulating, it is noticeable that the amount of vertical displacement of the exerciser's c.g. it not effected by his climbing rate. By walking or running 100 feet along a slope of 35.degree. he will raise c.g. 57 feet no matter how fast he moves. Moreover, his rate of oxygen consumption (which is the measure of energy output) will (according to the Bobbert equation expressing observed data) follow quite closely his stepping rate (velocity).
In order to have stair-climbing simulation equipment more closely produce the exercise results of actual slope climbing, and thereby obtain the benefits associated with the higher energy outputs at lower speeds (the inherent exercise advantage associated with climbing in comparison with other exercises) it is desireable to make the user's c.g. displacement less effected by the stepping rate than it is now in current equipment.